1. Field of the Invention
This invention relates to a rare earth-cobalt, RCo.sub.5 (R for rare earth elements and Co for cobalt) type magnetic powder suitable for a resinous magnet, which is produced by subjecting the oxides of the rare earth elements consisting of Sm as a main component and further of a first member comprising at least one element selected from between La and Ce and a second member comprising at least one element selected from between Pr and Nd, to the so-called reduction diffusion method, i.e. a procedure comprising the steps of first reducing the oxides with a reducing agent and diffusing the product of reduction in the cobalt powder.
2. Description of the Prior Art
The reduction diffusion method for producing a SmCo.sub.5 type magnetic powder has been proposed in the specification of Japanese patent application disclosure No. SHO 54(1979)-102,271, which method effects the production by mixing the oxide of Sm with a reducing agent such as metallic calcium and cobalt powder, heating the resulting mixture as held in a container in the normal-pressure atmosphere of an inert gas at a temperature in the range of 900.degree. to 1,100.degree. C., placing the resulting product of reaction in water thereby converting the product into a slurry, and treating this slurry with water and an aqueous acid solution. For use in the production of a sintered magnet by the steps of fine comminution, press forming, and thermal treatment, the magnetic powder obtained by the method just described proves to be more favorable in terms of magnetic property, cost, etc. than any of the magnetic powders obtained by the conventional electrolytic method and melting method. When this magnetic powder is used for the production of a resinous magnet, however, since the step of heat treatment involved in the production of the sintered magnet mentioned above cannot be performed after the magnetic powder is mixed with resin, the resinous magnet to be produced has very poor magnetic property and cannot fully manifest the advantage in terms of cost which would otherwise be brought about by the reduction diffusion method.
Moreover, generally in the manufacture of magnetic powder for use in the production of a resinous magnet, the desirability of realizing usability of the oxide of Sm of poor purity as the raw material for the purpose of lowering the cost of production has been finding growing recognition. The oxide of Sm having a low purity, however, contains La, Ce, Pr, and Nd as main impurities in addition to Sm as the principal metallic component of the oxide. The resinous magnet manufactured by the aforementioned reduction diffusion method using the oxide of Sm containing such defiling rare earth elements possesses an appreciably low magnetic property as compared with the resinous magnet manufactured using the oxide of Sm of high purity.